利用MOCVD技术在图形化Si(111)衬底上生长了InGaN/GaN绿光LED外延材料。在GaN量子垒的生长过程中, 保持NH3流量不变, 通过调节三乙基镓(TEGa)源的流量来改变垒生长速率, 研究了量子垒生长速率对LED性能的影响。使用二次离子质谱仪(SIMS)和荧光显微镜(FLM)分别对量子阱的阱垒界面及晶体质量进行了表征, 使用电致发光测试系统对LED光电性能进行了表征。实验结果表明, 垒慢速生长, 在整个测试电流密度范围内, 外量子效率(EQE)明显提升。我们认为, 小电流密度下, EQE的提升归结为量子阱晶体质量的改善; 而大电流密度下, EQE的提升则归结为阱垒界面陡峭程度的提升。

采用MOCVD技术在硅衬底上生长了含有7个黄光量子阱和1个绿光量子阱的混合有源区结构的InGaN基黄绿双波长LED外延材料, 研究了电子阻挡层前p-GaN插入层厚度对黄绿双波长LED载流子分布及外量子效率 (EQE) 的影响。通过LED变温电致发光测试系统对LED光电性能进行了表征。结果表明, 100 K小电流时随着电流密度的增大, 三组样品的绿光峰与黄光峰相对强度的比值越来越大, 且5.5 A·cm-2的电流密度下, 随着温度从300 K逐步降低至100 K, 三组样品的绿光峰与黄光峰相对强度的比值也越来越大, 说明其载流子都在更靠近p型层的位置发生辐射复合。三组样品的p-GaN插入层厚度为0, 10, 30 nm时, EQE峰值依次为29.9%、29.2%和28.2%, 呈现依次减小的趋势, 归因于p-GaN插入层厚度越大, p型层越远离有源区, 空穴注入也越浅。电子阻挡层前p-GaN插入层可以有效减小器件EL光谱中绿光峰随着电流密度增加时峰值波长的蓝移 (33 nm), 实现了对低温发光光谱的调控。

应用坩埚下降法生长了Pr3+离子掺杂的Na5Lu9F32单晶体.系统地研究了Pr3+掺杂的Na5Lu9F32单晶的吸收光谱、荧光光谱和荧光衰减曲线.应用Judd-Ofelt理论分析计算了其光学强度等参数, 结果表明Pr3+离子处于Pr-F强共价键的高对称环境中.在440 nm光的激发下观察到以482、523和605 nm为中心的尖锐的强荧光发射带.研究了Pr3+掺杂浓度对上述发光强度的影响规律, 实验发现当Pr3+掺杂浓度达到~0.5 mol%时, 其荧光发射强度达到最大.分析了环境温度从298 K到443 K变化时对荧光强度的影响, 随着温度的增加, 荧光强度逐步变弱, 且其523 nm的绿光受温度影响要小于482 nm的蓝光和605 nm的红光.

High-quality KMgF3 single crystal containing 0.5 mol% europium (Eu) was prepared by an improved Bridgman method. X-ray diffraction (XRD), photoluminescence spectra and fluorescence lifetime were measured. The results in-dicate the reduction of Eu3+ to Eu2+ in the KMgF3 single crystal. Under the excitation of 259 nm, 370 nm and 394 nm, the sample has two distinct emissions of Eu2+:4f7→4f7(~363 nm) and 4f65d1→4f7 (~440 nm). The substitution site for Eu ion is confirmed. The optical property investigation result shows that the Eu2+ doped KMgF3 single crystal may be used as potential laser media and related materials for optical devices.

The growth of Na5Lu9F32 single crystals doped with Cr3+ ions in 0.1 mol%, 0.2 mol% and 0.5 mol% concentrations by Bridgman method was reported. The optical absorption and luminescence spectra decisively demonstrate that the Cr dopant enters Na5Lu9F32 as Cr3+. Fluorescence emission at wavelengths of 418 nm, 444 nm, 653 nm and 678 nm can be observed under the excitation of 372 nm and the fluorescence lifetime at 418 nm was measured to be ~10.31 μs. The possible crystal sites for Cr3+ ions in Na5Lu9F32 single crystal were discussed, and the lattice parameter Dq, Racach parameters B and C were estimated.

Tm3+ doped Na5Lu9F32 single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters Ωt (t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na5Lu9F32 single crystal. The stimulated emission cross-section of the 3F4→3H6 transition (~1.8 μm) is 0.35×10-20 cm2 for Tm3+ doped Na5Lu9F32 single crystal. The emission spectra under the excitation of 790 nm laser diode (LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm3+ doped Na5Lu9F32 single crystal. The research results show that the Tm3+ doped Na5Lu9F32 single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm3+doped Na5Lu9F32 crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.

采用MOCVD技术在图形化硅衬底上生长了InGaN/GaN多量子阱黄光LED外延材料, 研究了不同的量子阱生长气压对黄光LED光电性能的影响。使用高分辨率X射线衍射仪(HRXRD)和荧光显微镜(FL)对晶体质量进行了表征, 使用电致发光系统积分球测试对光电性能进行了表征。结果表明: 随着气压升高, In的并入量略有降低且均匀性更好, 量子阱中的点缺陷数目降低, 但是阱垒间界面质量有所下降。在实验选取的4个气压4, 6.65, 10, 13.3 kPa下, 外量子效率最大值随着量子阱生长气压的上升而显著升高, 分别为16.60%、23.07%、26.40%、27.66%, 但是13.3 kPa下生长的样品在大电流下EQE随电流droop效应有所加剧, 在20 A·cm-2的工作电流下, 样品A、B、C、D的EQE分别为16.60%、19.77%、20.03%、19.45%, 10 kPa下生长的量子阱的整体光电性能最好。

采用实验与理论模拟相结合的方法, 研究了氮化镓基绿光发光二极管(LED)中V坑对空穴电流分布的影响。首先, 实验获得了V坑面积占比不同的3种样品; 然后, 建立数值模型, 使得理论计算的外量子效率(EQE)及电压与实验测试的变化趋势相匹配, 从而确立了所用数值模型的可信性。计算结果显示: V坑改变了空穴电流的分布, 空穴电流密度在V坑处显著增加, 在平台处明显减小。进一步的分析表明: V坑面积占比在0~10%范围内, V坑空穴电流占比与V坑面积占比之间呈近线性增长(斜率为2.06), 但V坑空穴注入在整个空穴注入的过程中仍未占主导。

采用改进过的布里奇曼法成功地生长了Tm3+离子浓度从0.5～4 mol%变化的高质量Na5Lu9F32单晶.在790 nm LD激发下, 研究了不同Tm3+掺杂晶体在1.86 μm波段的荧光发射性能、衰减曲线以及Tm3+离子之间的能量传递过程.当Tm3+离子掺杂浓度增加到~1.95 mol%时, 晶体在1.86 μm处的荧光发射强度达到最大.然后, 随着Tm3+离子浓度进一步的增大, 发射强度迅速下降.然而, Tm3+离子在3F4能级处的荧光寿命随着Tm3+掺杂浓度从0.5增加到4 mol%, 逐渐降低.同时计算了1.86 μm处最大的受激发射截面为0.80×10－20 cm2.Tm3+离子的浓度猝灭效应和离子之间的交叉弛豫能量传递过程是造成1.86 μm荧光发射变化的主要原因.

Tm³⁺doped Na₅Lu₉F₃₂single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters Ω_t(t=2, 4, 6) were calculated according to the measured absorption spectra and physical- chemical properties of the obtained Na₅Lu₉F₃₂single crystal. The stimulated emission cross-section of the ³F₄→³H₆transition (~1.8 μm) is 0.35×10^-20cm²for Tm³⁺doped Na₅Lu₉F₃₂single crystal. The emission spectra under the excitation of 790 nm laser diode (LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm³⁺doped Na₅Lu₉F₃₂single crystal. The research results show that the Tm³⁺doped Na₅Lu₉F₃₂single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm³⁺doped Na₅Lu₉F₃₂crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.